Down-hole drilling and oil/gas production operations, such as those used to extract crude oil from one or more production zones in the ground, often utilize long lengths of production tubing to transmit fluids from great depths underneath the earth's surface to a well head above the surface. Such systems often use screens of various types to control the amount of particulate solids transmitted within the production fluid. It is well known that screens are designed to surround perforated portions of the production tubing or a perforated production sub, so that fluids and gases may enter the production tubing while leaving undesirable solids, such as formation sand, in the annulus. These screens may be used in either open-hole or cased-hole completions.
A disadvantage of current generation screens is the inability to control flow rate of the production fluid. Such screens operate as static devices in that they do not allow for an increase or decrease in the fluid flow area through the screen.
Other prior art screens have variable flow areas. A disadvantage of these screens is their relatively small flow area, which can lead to a reduced rate of production fluid flow.
Another disadvantage associated with some prior art screens is the requirement that flapper valves be used to control fluid loss prior to production. Flapper valves are prone to cracking or breaking such that pieces of the flapper valves may be introduced into areas of the well causing damage or interfere with various well components such as, for example, the chokes, sensors and other devices, in the well.
Still another disadvantage associated with some prior art screens is the use of ball sealers to shut off perforations through which excessive fluid is being lost. The use of ball sealers require special running tools and ball catchers, which may restrict the wellbore thus reducing production. Additionally, ball sealers introduce additional complexity and cost to the oil production operation.
Considering the foregoing disadvantages associated with prior art screening systems, a cost effective non-intrusive means of achieving variable control of the flow area provided by a well screen would provide numerous advantages.